Sixteen patients with idiopathic hypoparathyroidism (IHP) and eight patients with pseudohypoparathyroidism (PHP) were examined by CT scan of the brain. Calcification in the basal ganglia was observed in 11 patients with IHP (69%) and in all eight patients with PHP. Of the 19 patients with basal ganglia calcification, nine had calcification in the cerebral cortex (47%), and four had calcification in the cerebellum (21%). Observation of basal ganglia calcification on CT gave rise to suspicion of IHP or PHP in three patients (12%). The remaining patients were examined at varying time after diagnosis. Since arrest in growth of calcification after institution of treatment has never been proven, the reported prevalences of calcification may not be valid to the situation at the time of diagnosis.